Revert a workaround commit for a UAF crash.

chrome/browser/net/chrome_url_request_context.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_NET_CHROME_URL_REQUEST_CONTEXT_H_
 #define CHROME_BROWSER_NET_CHROME_URL_REQUEST_CONTEXT_H_
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 23 matching lines @@
     CONTEXT_TYPE_MAIN,
     CONTEXT_TYPE_MEDIA,
     CONTEXT_TYPE_EXTENSIONS,
     CONTEXT_TYPE_APP
   };
   ChromeURLRequestContext(ContextType type,
                           chrome_browser_net::LoadTimeStats* load_time_stats);
   virtual ~ChromeURLRequestContext();
 
   base::WeakPtr<ChromeURLRequestContext> GetWeakPtr() {
-    return base::AsWeakPtr(this);
+    return weak_factory_.GetWeakPtr();
   }
 
   // Copies the state from |other| into this context.
   void CopyFrom(ChromeURLRequestContext* other);
 
  private:
+  base::WeakPtrFactory<ChromeURLRequestContext> weak_factory_;
+
   // ---------------------------------------------------------------------------
   // Important: When adding any new members below, consider whether they need to
   // be added to CopyFrom.
   // ---------------------------------------------------------------------------
 
   chrome_browser_net::LoadTimeStats* load_time_stats_;
 
   // ---------------------------------------------------------------------------
   // Important: When adding any new members above, consider whether they need to
   // be added to CopyFrom.
@@ skipping 91 matching lines @@
 
   // NULL if not yet initialized. Otherwise, it is the ChromeURLRequestContext
   // instance that was lazily created by GetURLRequestContext().
   // Access only from the IO thread.
   base::WeakPtr<ChromeURLRequestContext> url_request_context_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeURLRequestContextGetter);
 };
 
 #endif  // CHROME_BROWSER_NET_CHROME_URL_REQUEST_CONTEXT_H_